High manganese brass alloys



Aug. 23,-1949. E. A, ANDERSON ET AL 2,479,595

HIGH MANGANESE BRASS ALLOYS 3 Sheets-Sheet l Filed Deo. 20, 1.947

. lNvENToRs o/wwvp A A/JERsa/v A wa /LA 50N ATTORNEYS Aug. 23, 1949.

Filed' Deo. 20. 1947 TEA/.SME 2m/GA NoN-Z /A/ 2 E. A. ANDERSON ET Al. 2,479,595

HIGH MANGANESE BRASS ALLQYS 3 Sheets-Sheet 2 M, Q/m

ATTORNEYS Aug. 23, 1949. E. A ANDERSON ET Al. *2,479,595

HIGH MANGANESE BRASS ALLOYS Filed Deo. 20, 1947 5 Sheets-Sheet 5 ATTO RNEYS Patented ug. 23, 1949 HIGH MANGANESE BRASS ALLOYS Edmund A. Anderson and erton, Pa., assignors to Company, New York,

New Jersey David C. Jillson, Palm- The New Jersey Zinc N. Y., a corporation of Application December 20, 1947, Serial No. 792,966

Claims.

This invention relates to alloys and, more particularly, to high manganese brass alloys characterized by high tensile strength and high elongation as well as by excellent retention of composition during remelting.

Manganese brasses, that is copper-Zinc-manganese alloys, have been known for decades. In general, the tensile strength of manganese brasses increases, and the ductility decreases, with increasing manganese content. The increasing use of high manganese brasses, containing upwards of 7-8% manganese, has given considerable impetus to the quest for such alloys of maximum tensile strength and ductility. Manganese brasses of excellent tensile strength have been produced heretofore but they have been characterized by low ductility and have therefore lacked the ability to resist mechanical shock without the likelihood of failure. v

Numerous metals have been proposed heretofore as additional components for manganese brasses. The principal object in adding such additional metals has been to increase the tensile strength of the manganese brass, but most of the added elements proposed heretofore have reduced the ductility as they have increased the tensile strength. A common and reliable index oi the ductility of a metal is its percentage elongation when subjected to tensile strength tests, higher tensile elongation representing higher ductility and vice versa.

A notable disadvantage in the properties of high manganese brasses has been the tendency for the manganese to selectively oxidize during melting and casting operations and thus introduce into the castings sizable occlusions of manganese oxide. These occlusions weaken the articles fabricated from the alloy. Moreover, the mechanical properties of the alloys, which are largely determined by the manganese content, are altered to the extent that the manganese content of the alloys is decreased by its loss in the form of manganese oxide.

In the copending application of John L. Rodda, Serial No. 541,399, led June 24, 1944, now abandoned, there are described high manganese brasses containing from 15 to 37.5% Zinc, from 7.5 to 30% manganese, from 0.25 to 2% silicon, from 0.1 to 2% aluminum, and the balance copper. As pointed out in said application, the silicon and aluminum function as anti-oxidants capable of preventing oxidation of the manganese during production of the alloy and its subsequent remelting. The application also points out that up to about 1% silicon increases the tensile strength of the alloy at the expense of some loss in tensile elongation, and it is also stated that up to about 2% aluminum improves the tensile strength but decreases the tensile elongation of the alloys. Thus, although the alloys described in said application are characterized by high tensile strength, their ductility is low, the tensile elongation varying from about` 5 to about 20 in two inches. i.

We have now found that high manganese brasses of excellent tensile strength and ductility may be obtained by the incorporation therein of the proper amounts of both silicon and aluminum. Within certain definite limits, the silicon increases the tensile strength of the alloys with a consequent reduction in the ductility thereof. The aluminum, when used in conjunction with the silicon, materially increases the ductility of the alloys without detracting from the high tensile strength imparted thereto by the silicon. Both silicon and aluminum, and particularly the aluminum, behave as anti-oxidants in the high manganese brasses and largely inhibit the selective oxidation of manganese during remelting of the alloys. The silicon and aluminum thus make possible the production of high manganese brass alloys characterized by high tensile strength and ductility and further characterized by retention of their composition upon remelting. VThis retention of composition upon remelting is a measure of the freedom of the cast and fabricated alloy articles from detrimental occlusions of manganese oxide and is also a measure of the predictability oi the mechanical properties of the cast and fabricated alloy articles.

The high manganese brasses contemplated by the invention consist of copper, zinc, manganese, silicon and aluminum. A characteristic feature of these silicon-containing manganese brasses is their freedom from iron. As a result of extensive investigation, we have found that the beneiicial effect of silicon, as enhanced by the further presence of aluminum, can be obtained only when the amount of iron present in the alloy, and introduced generally as an impurity, is maintained below a very small permissible maximum. Iron in excess of this specified amount appears to combine with the silicon-to form intermetallic compounds which cause embrittlement of the manganese brass alloys and thus substantially destroy their utility.

In general, the manganese brasses of the present invention contain from 55 to '72% copper, from l0 to 24% zinc and from 8 to 31% manganese within certain speciiied combinations of proportions as hereinafter more fully defined. We have found that the tensile strength of these manganese brasses is capable of improvement by from 0.25 to 1% silicon. Increasing amounts of silicon from 0.25 to 0.5% increase the tensile strength of the manganese brass and lower its tensile elongation. Further increasing amounts of silicon from about 0.5 to 1% appear to effect little further change in the tensile strength or tensile elongation of the alloys. s Increasing amounts of silicon above 1% rapidly cause embrittlement of the alloy even in the presence of alu- 3 minum. We havev'fou-nd that amounts of silicon between 0.5 and 0.75%, and preferably an amount of about 0.75%, produce manganese brasses of maximum tensile strength consistent with good tensile elongation.

Within the broad eifective range of silicon content of 0.25 to 1%, and particularly Within the optimum effective range of 0.5 to 0.75% silicon, we have found that a definite vrelationship between the copper, zinc and manganese components of the alloy exists for. alloys exhibiting the most desirable response to improvement in tensile elongation, as Well as high tensile strength, by the addition of aluminum. These proportions of copper, zinc and manganese are represented by the area ABCDA on the trilinear chart comprising Fig. l of the drawings. The manganese brass alloys Within this area, when further containing about 0.75% silicon and 0.5% aluminum, have a tensile elongation of or higher in addition to a relatively high tensile strength. The relative proportions of copper, zinc and manganese of particularly useful alloys in accordance with the invention are those coming Within the area EFGHE in Fig. 1, these alloys, when containing about 0.75% silicon and 0.5% aluminum, having a tensile elongation of at least in addition to high tensile strength. The following table gives the analyzed composition and mechanical properties of several alloys having compositions Within the area ABCDA in Fig. 1, these specic examples being typical of those which We have found to be susceptible to the desired improvement by the addition of silicon and aluminum. The tensile elongation of many of the alloys Within the areaABCDA, and particularly those within the smaller area EFGHE, may be substantially increased by the use of a diierent amount of aluminum as hereinafter explained.

of uniformity,` the ratio of lzine to manganese was maintained at substantially 1.15 to 1, although it must be understood that the alloys of the inven` tion are by no means limited to such a ratio. Each of the alloys contained 0.75% silicon. It will be seen that the alloys containing 60, 65 and 70% copper, respectively, each showed a maximum tensile elongation at a Well-defined aluminum content. The alloy containing 75% copper exhibited a wholly different ductility response to the addition of aluminum, thus indicating that the alloy containing 75% copper is of a fundamentally different type than the other alloys of lower copper content. We have found that the manganese brasses of the present invention, con taining up to approximately 72% copper, exhibit the property of responding with a Well-dencd maximum tensile elongation for a specic aluminum content. Based upon a series of curves such as those shown in Fig. 2, the curve AB in Fig. 3 shows the amount of aluminum which will produce maximum tensile elongation with any copper content from to 72% copper in the alloys of the invention.

lThese optimum amounts of aluminum produce a maximum tensile elongation of at least 24% in all of the silicon-containing manganese brasses ci the present invention. In View of the fact that commercially satisfactoryalloys may be tolerated having a percentage tensile elongation approximately 5 less than the maximum obtainable in accordance with the invention, there are also plotted in Fig. 3 greater and lesser amounts of aluminum which may be used with varying fg copper content to produce alloys having a percentage tensile elongation about 5 less than the maximum obtainable with the optimum amount of aluminum. Thus, ratios of aluminum to copper coming Within the area embraced by the lines Analyzed Composition Mechanical Properties Per Per Per Per Per Tensile egt l'aof Brlnell Cent Cent Cent Cent Cent Strengt Elong Per Hardness Cn 'Zn Mn Si .A1 p. s. 1. in 2 Cent Number 65. 1 19. 1 14. 7 Q. 67 0. 5 65, 000 20 16 93 61. 1 20. 9 17. 2 0. 64 0. 65 66, 900 32 28 110 65. 3 16. 0 18. 9 0. 78 0. 25 71, 000 21 17 95 65. 4 18. 6 15,. 5 0. 75 0. 25 64, 200 16. 3 ll. 9 93 65. 6 22.1 12.0 0. 77 0. 22 60, 800 15 11. 1 90 61. 6 16. 7 20. 8 0.76 0.25 73, 100 21. 1 17. 7 98 00. 2 20.8 17. 7 0. 7,4 0. 24 68, 100 21. 8 17. 3 94 56. 8 18. 2 24. 2 0 74 0. 25 72, 100 17. 5 13. 7 104 56. 8 22. 7 19.' 6 0. 76 0. 24 69, 200 17. 5 12. 8 99 We have found that in manganese brasses of the above-described ranges and relationship of copper, zinc and manganese and containing silicon wit'hin the specined limits, there exists a definite relationship between the amount of aluminum and the amount of copper present in the alloy for the production of optimum tensile elongation. Thus, We have found that in these silicon-containing manganese brasses characterized by high tensile strength, and containing any iixed amount of copper Within the range of 55 to 72% copper, increasing amounts of aluminum rst produce an increase in the tensile elongation of the alloys and then tend to decrease the elongation. This effectis shown in Fig. 2 of the drawings Wherein there is plotted the tensile elongation with increasing amounts of aluminum for each of four alloys yof different copper content. s indicated in the drawings, the copper contents of the four alloys are.60%, 65%, 70% and 75 respectively. In each of the alloys, for the sake 75 CD and EF in Fig 3 are characterized by high tensile strength and a tensile elongation of at least 19%.

Although the silicon content of the alloys of the invention, that is, up to about 1% silicon, tends to inhibit oxidation of the manganese of the alloy during manufacture, remelting and casting, we have found that the presence of aluminum in the amount of at least 0.15% is still more effective than the silicon for this purpose. Thus, high manganese brasses of the invention containing both silicon and aluminum are charN acterized by excellent retention of composition while the alloy is in its molten state. For example, an alloy consisting nominally of 60% copper, 21% zinc, 18% manganese and 1% silicon, without any aluminum, was chemically analyzed and found to contain 16.6% manganese. The alloy was then heated to a temperature substantially above its melting temperature, the metal Was skimmed thoroughly, a water-pour sample was taken for analysis, and the remainder of the alloy was cast. The cast alloy was again remelted in the same manner, and this procedure was repeated until the alloy had been remelted a total of four times. Analysis of the water-pour sample taken at the end of each remelting operation showed that the manganese content of the alloy decreased from the original 16.6% to a nal 13.9%. Part of the manganese thus lost appeared as a brown manganese oxide scum and was largely removed from the surface of each melt. The remainder of the manganese lost was oxidized during casting and this oxide, plus that remaining as a scum on the surface of the melt, largely appeared in the form of occlusions in the cast metal. Another alloy of the same nominal composition except that it contained 0.50% aluminum in lieu of the silicon was similarly subjected to four remelting operations. The manganese analyses on the water-pour samples of this alloy showed a decrease from 17.1% manganese prior to the first remelt to 16.7% manganese after the fourth remelt. Still another alloy of the same composition except that it contained 0.8% silicon and 0.5% aluminum, with the balance consisting of copper, zinc and manganese, was similarly treated. Its manganese content remained constant at 17.4% manganese throughout the four remelting operations.

It will be seen, acordingly, that the high manganese brasses of the present invention are characterized by high tensile strength and ductiliti7 and are further characterized by retention of their composition during remelting. The alloys of the invention consist of copper, zinc, manganese, silicon and aluminum, the amount of copper, Zinc and manganese being such as to come within the area ABCDA in Fig. 1 of the drawings, the silicon content ranging between 0.25 and 1%, and the aluminum being present in amount with respect to the copper such as to come within the range of proportions defined by the area between lines CD and EF in Fig. 3 of the drawings. However.` as pointed out hereinabove, we have found that the attainment of high ductility in these alloys of high tensile strength depends upon the substantial exclusion of iron therefrom.

Iron is a common impurity in commercial manganese. Analyses of manganese metal used in the preparation of alloys show that iron is generally present to the extent of at least several per cent. Even the best grades of manganese produced according to commercial practice contain approximately 1.5% or more of iron. In our early investigations with respect to the use of silicon in high manganese brasses such as those of the present invention, it was found that the presence of silicon caused embrittlement of alloys produced with even the best commercial grades of manganese. It was only by using electrolytic manganese, which is substantially completely free from iron, that We found the silicon to be capable of increasing the tensile strength of these manganese brasses without causing extensive embrittlement thereof. As a result of our investigation of this matter, we have found that when silicon is present in the manganese brasses of the present invention in amounts ranging between 0.25 and 1% silicon, the alloys cannot contain more than 0.16% iron without causing embrittlement. The permissible amount of iron, that is, up to 0.16%, shows no beneficial effect and appears in the final alloys only because of its presence as an impurity in the other component elements of the alloy. The effect of the presence of up to 0.24% iron in a manganese brass alloy of the invention consisting of about 60% copper, about 21% zinc, about 18% manganese, about 0.75% silicon and 0.5%, is shown in Fig. Il of the drawings. In this figure there is ploted the tensile elongation of the alloy with increasing percentages of iron. It will be seen that the presence of up to about 0.12% iron has no appreciable effect upon the tensile elongation of the alloy. Between 0.12 and 0.16% iron the tensile elongation of the alloy starts to decrease, becoming precipitous at about 0.16% iron content. Thus, although aluminum is present in the alloy in substantially the optimum amount required to obtain maximum tensile elongation for this high tensile strength alloy, the aluminum is unable to overcome the deterimental effect of the iron when the iron content exceeds 0.16%.

Accordingly, the metals used in perparing the alloys of the invention-should be of sufficiently high purity to avoid the introduction into the alloy of iron in amounts of about 0.16% or higher. Electrolytic manganese is the preferred source of the manganese constituent, although special grades of aluniino-thermic and other special pyrolytioally prepared manganese may be used where the iron content thereof is sufficiently small to permit use of such manganese metal without introducing more than the critical limit of iron into the alloy. Electrolytic copper cathode sheet, or any other good commercial grade of copper, may be used in the manufacture of the alloys of the invention. The zinc is preferably high grade metal containing 99.99% Zinc.

rlhe alloys of the invention are preferably manufactured and handled in clay-silicon carbide and carbon-silicon carbide crucibles. Steel crucibles should be avoided in the manufacture of the alloy. Crucibles made of refractory oxides, such as alumina and'magnesia, may be used with advantage.

In manufacturing the alloy, the copper is first melted and brought to a sufficiently high temperature so as not to freeze when the other alloying constituents are later added. The manganese is then added in small lots until all of the addition has dissolved in the copper. At this stage, it is expedient to add a small amount of borax to clear up the oxide on the surface of the melt. The amount of borax is preferably less than that required to form' a continuous molten cover, the ideal condition being to have beads of molten borax which dissolve or flux the surface oxide and then gather near the crucible wall leaving a clear center portion through which other additions may be made. After the borax has thus cleared up the oxide on the surface of the melt, the zinc and silicon (the latter as a copper-silicon "hardener alloy containing about 15% of Silicon) are plunged into the melt, and the entire melt is stirred to produce a uniform composition. The aluminum is next added in small pieces placed on the surface of the melt and allowed to dissolve quietly without stirring. This procedure gives a higher recovery of aluminum in the final melt than is otherwise obtained by plunging the aluminum below the melt surface. The inal operations are to stir thoroughly, allow the melt to stand for a few minutes to permit entrained oxides to reach the surface, and then skim and pour.

The alloys of the invention melt at temperatures between about 800 and 900 C. The variation in melting temperature with variation in the copper-zinc-manganese proportions is shown by 7 the dottedline contours of melting points appearing in Fig. 1. Although these alloys require a superheat generally of the order of 50 to 100 C. above the melting point in order to produce satisfactory castings, the alloys of the invention, containing both silicon and aluminum, are stable in composition for long periods of time at temperatures of the order of 1000 C. Accordingly, the alloys of the invention have melting points sunciently low to permit adequate superheating for perfect casting without losing the oxidationinhibitory effect of the amounts of silicon and aluminum used'in accordance with the invention.

The alloys of the invention can be sand cast quite easily in the standard green sand mold common to the foundry industry, using casting and molding practices common in the industry. The Valloys have a high shrinkage during solidication, as have manyrsand casting alloys, and means for handling such alloys are well understood and available in commercial foundry practice. A notable advantage of the alloys in sand casting is that the sand does not adhere thereto and can be removed easily by shaking or by blowing, as distinguished from most commercial foundry alloys which must be sand blasted to remove the sand burned into their surfaces during the casting operation.y In addition to sand casting, the alloys of the invention may be chill cast or die cast.

The machinability of the manganese brasses of the invention may be Vimproved by the common expedient of adding lead thereto. For this purpose, up to about 3% lead, and preferably about 2% lead, may be incorporated in the alloys.

A further noteworthy property of the alloys of the invention (particularly of alloys containing 1823% zinc, 15-20% manganese, G25-1% silicon, 0.2'-;5% aluminum, and 55u-'67% copper) is the retention of their excellent physical properties at elevated temperatures. .Thus the tensile strength, tensile elongation and yield strength (stress producing 0.5% deformation under load) of the alloys are substantially unchanged from room temperature up to temperature of 500 F. Above 500 F. and up to 800 F., the tensile strength decreases somewhat, the tensile elongation increases appreciably, and the yield strength undergoes little change. These properties are outstanding when compared with va common bronze (88% copper,8% tin, and 4% zinc), as will be seen from an inspection of the following table:

Alloy of Invention A. Common Bronze Temp., F.

Tensile Tensile Elon- Tensile Tensile Elon- Strength gatlon Strength gation per in said zinc, manganese, silicon and aluminum, the amount of copper, zinc and manganese being such as to come within the area ABCDA in Fig. 1 of the drawings, the silicon content ranging between 0.25 and 1%, and the aluminum being present in amount with respect to the copper such as to come within the range of proportions defined by the area between lines CD and EF in Fig. 3 of the drawings, said alloy being substantially free of iron in excess of 0.16%.

2. A vhigh manganese brass alloy characterized by high tensile strength and ductility and further characterized by retention of composition during remelting, said alloy consisting of copper, zinc, manganese, silicon and aluminum, the amount of copper, zinc and manganese being such as to come within the area ABCDA in Fig. lof the drawings, the silicon content ranging between 0.5 and 0.75%, and the aluminum being present in amount with respect to the copper such as to come within the range of proportions defined by the area between lines CD and EF in Fig. 3 of the drawings, said alloy being substantially free of iron in excess of 0.16%.

3. A high manganese brass alloy characterized by high tensile strength and ductility and further characterized `by retention of composition during remelting, said alloy consisting of copper, zinc, manganese, silicon and aluminum, the amount of copper, zinc and manganese being such as to come within the area ABCDA in Fig. 1 of the drawings, the silicon content ranging between 0.25 and 1%, and the ratio of aluminum to copalloy being defined by the line AB in Fig. 3 of the drawings, said alloy being substantially free of iron in excess of 0.16%.

4. A high manganese brass alloy characterized by high tensile strength and ductility and further characterized by retention of composition during remelting, said alloy consisting of copper zinc, manganese, silicon and aluminum, the amount of copper; zinc and vmanganese being such as to come within the area ABCDA in Fig. 1 ofthe drawings, the silicon content ranging between 0.5 and 0.75%, and the ratio of aluminum to copper in said alloy being defined byV the line AB in Fig. 3 of the drawings, said alloy being substantially free'of iron in excess of 0.16%.

5. A high manganese brass alloy characterized by high tensile strength and ductility and further characterized by retention of composition during remelting, said alloy consisting of copper, zinc,` manganese, silicon and aluminum, the amount of copper, zinc and manganese -being such as to come within the area EFGHE in Fig. 1 of the drawings, the silicon content ranging between 0.5 and 0.75%, and the ratio of aluminum to copper in said alloy being defined by the line AB in Fig. 3 of the drawings, said alloy being sub'- stantially free of iron in excess of 0.16%

EDMUND A. ANDERSON. DAVID C. JILLSON.

REFERENCES CITED UNITED STATES PATENTS NameY Date Ray El? 2,1 ...0017, 31, 1933 OTHER REFERENCES Engineering Alloys, by Woldman, 1936 ed., pages 176 and 177.

Number Certificate of Correction Patent No. 2,479,595 August 23, 1949 EDMUND A. ANDERSON ET AL. It is hereby certied that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 6, line 4, after 0.5% and before the comma insert the Word aluminum and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 27th day of December, A. D. 1949.

THOMAS F. MURPHY,

Assistant Oommzss'ioner of Patents. 

